It's the new riddle of the Sphinx: "Why didn't he call me back?" You have a great first date with a promising guy. You think it went well and expect to see him again… but then poof! He vanishes inexplicably. You sit around with your girlfriends and debate why he didn't call you back. What happened in between "I'll pick you up at 8pm" and "poof?" You speculate, you obsess, you rationalize, you justify. You want to know why. When your friends tell you, "It's not you, it's him," you want to know if they're trying to be nice or telling you the truth.

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Guess what? There is someone who does know the truth about what really happened on your date. But it's not you. It's not your friends. And it's certainly not your mother. It's the guy you went out with. So I decided to ask him for you! In fact, I asked 1,000 "hims." During the past ten years as a dating coach and matchmaker, I conducted "exit interviews" with 1,000 single guys to find out why you never heard from him again after a date, or after he flirted with you online or at a party. And I got some real answers. It turns out there are clear, consistent reasons why men show initial interest and then disappear. Sure, sometimes the issue is all his—who hasn't gone out occasionally with a real jerk? But it turns out that many times we're sending out signals we might not be aware of. And the good news is that most of these signals are easy to fine-tune.

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Men essentially confessed that when they first meet you, they have several "female stereotypes" floating around in their mind. They quickly try to peg which stereotype you are and then look for evidence to back up their hunch. You know who you are deep down, but he doesn't yet. So he will decide whether to call you again based on his perception of you, not the reality. In the early stage of dating, perception is reality. Here are three of the most common reasons men revealed why they aren't calling women back (get the other 7 reasons - and what you can do about all of them - in my new book).

Reason #1: The Boss Lady

His perception: He'd rather hire you than date you. He perceives you as argumentative, controlling, overly independent, and not feminine or warm. While you think he's intimidated by your success, he's thinks you have a prickly attitude and imagines that snuggling with you is like hugging a porcupine in a pin-striped business suit!

Your reality: You're confident, forthright and successful, but he can't yet see those great qualities behind your tough demeanor. Try showing your warm, sensitive side first by talking about your adorable nephew or your volunteer work at the animal rescue shelter. And definitely change clothes after work into a flirty skirt instead of staying in that power business suit.

Reason #2: The Park Avenue Princess

His perception: You're looking for a "Perfect 10": the guy's who's a 5 on the looks scale with $5 million in the bank. He thinks you're high maintenance, superficial, or a gold-digger.

Your reality:You can take care of yourself. You enjoy spending what you make. Maybe you're interested in a nice lifestyle, though it's not your only priority. But he's jaded by all the gold-diggers he dated before you (you're guilty until proven innocent). So instead of asking him "What's your favorite hotel in St. Bart's?" you should ask "What's your favorite little neighborhood café?" When the waiter inquires whether you'd like tap or bottled, don't order the Evian; one glass of city water (almost) never killed anyone! {Tip: squeeze a little lemon in your glass…}

Reason #3: The Sadie Hawkins

His perception: You're pursuing him. You sent him a thank-you email after your date, and immediately he knew you liked him. He may even think you're a little desperate. Deep down, he feels deflated because when he likes a woman, he'd rather do the chasing.

Your reality: That thank-you email was a show of good manners, not a subtle hint for him to ask you out again. At work you're rewarded for taking initiative, but with guys you have to let them reach out first. Don't say, "Let's do this again sometime"—that's his line. This is one time in your empowered, take-charge life when you have to sit back and wait after a first date—do absolutely nothing to follow-up (don't even check to see if he's logged into his online dating profile). He's a big boy and knows how to contact you if he's interested.

I truly believe it's not that "good" guys don't exist, but rather that simple (mis)perceptions—which can be easily tweaked once you're aware of them—are standing in Cupid's way. Which stereotype do you think men might be labeling you? There's only one way to find out: learn how to conduct your own personal "exit interviews!" at www.whyhedidntcallyouback.com

Rachel Greenwald is the author of Why He Didn't Call You Back: 1,000 Guys Reveal What They Really Thought About You After Your Date. She is also the New York Times Bestselling author of Find a Husband After 35 (Using What I Learned at Harvard Business School). Rachel is a frequent relationship guest on The Today Show, The Early Show, CNN, National Public Radio, and has been featured in Oprah Magazine, Fortune Magazine, The New York Times, People, USA Today, and many others. She is a professional dating coach and matchmaker.